Pack cosmetics have been widely used in cosmetic products and quasi-drugs from old times. The use thereof is not only for faces but also widely spreads over topical use for necks, shoulders, arms, and legs as well as systemic use. The primary object to use pack cosmetics is to cover skins with a coating for a certain period of time, thereby imposing the moisture retentivity on skins and causing effective penetration through skins of drug components compounded in the coating. An available pack cosmetic is polyvinyl alcohol. The polyvinyl alcohol has an excellent coating formability and can achieve such the object. Accordingly, it has been compounded in many pack cosmetics previously (Patent Document 1). The polyvinyl alcohol, however, increasingly decomposes over time and lowers the pH of an aqueous solution as a problem.
Of pack cosmetics, packs of the sheet type in particular include a hydrous gelling agent developed as the base for poultices in the field of medicines. The hydrous gelling agent includes a water-soluble polymer capable of retaining water and specifically uses an acrylic acid-based polymer in general. If the carboxyvinyl polymer is used in formulae containing various salts, the thickening effect thereof may lower as a problem (Patent Document 2).
In recent years, ascorbic acid and derivatives thereof, and salts thereof (hereinafter referred to as ascorbic acid and analogues generally) are added as a whitening agent to impose the whitening effect on various cosmetics. The ascorbic acid and analogues are excellent in the whitening effect and stable in aqueous solution at a pH of about 6-9. In contrast, they are hardly stable in aqueous solution at a pH lower than 6 and cause variations in color and odor and occurrences of aggregations overtime as a problem. From such the consideration, it is difficult, with regard to the stability of the ascorbic acid and analogues, to compound ascorbic acid and derivatives thereof in the above-listed pack cosmetics containing polyvinyl alcohol as a problem. A method is developed to solve the problem, which comprises using a 2-O-D-glucopyranosyl-L-ascorbic acid derivative as a whitening effect component and compounding urea therewith (Reference 3).    Patent Document 1: JP 10-167951A    Patent Document 2: JP 2004-91360A    Patent Document 3: JP 2004-91360A